(a) Field of the Invention
The present invention relates to a display device and a sensing signal processing apparatus.
(b) Description of the Related Art
As a representative display device, a liquid crystal display (“LCD”) includes two panels which are respectively provided with pixel electrodes and a common electrode and a liquid crystal layer having dielectric anisotropy disposed therebetween. The pixel electrodes are arranged in a matrix shape, and each is connected to a switching element such as a thin film transistor (“TFT”) to sequentially receive an image data voltage row by row. The common electrode is formed over the entire surface of a display panel to receive a common voltage. The pixel electrode, the common electrode, and the liquid crystal layer therebetween constitute a liquid crystal capacitor. The liquid crystal capacitor and a switching element which is connected thereto become a basic unit which constitutes a pixel.
In the liquid crystal display, an electric field is generated in a liquid crystal layer by applying a voltage to the two electrodes of a pixel. Transmittance of light passing through the liquid crystal layer is adjusted by adjusting the intensity of the electric field. A plurality of pixels working together may thereby obtain a desired image.
A touch screen panel is an apparatus which writes or draws a character or a picture through contact with a finger, a pen, etc., on a screen. Touch screen panels may also allow a machine such as a computer to perform a desired command by executing a program when an icon is pressed. A liquid crystal display to which a touch screen panel is attached has two primary functions: determining whether a contact occurs, and determining the contact's position information. However, the addition of a touch screen feature to a liquid crystal display comes with the addition of problems such as an increase in the cost of a display, yield decrease due to the addition of a manufacturing process for bonding a touch screen panel on a liquid crystal panel, luminance deterioration of the liquid crystal panel due to the passage of light through an additional layer, an increase in product thickness, and other related problems.
Therefore, technology for providing a sensing element consisting of a thin film transistor within a pixel itself which displays an image in a liquid crystal display instead of an additional touch screen panel has been developed.
However, in the existing sensing elements it is very difficult to accurately determine whether a sensing element is operated, and a signal processing apparatus for processing a signal from the sensing element has a complicated structure, thus increasing an amount of signal processing time and manufacture costs.